Conditions such as osteoarthritis, deformity, cancer or trauma may cause degeneration of the articular surfaces between the trapezium and the first metacarpal as well as the other carpal and metacarpal bones in a hand. This causes the patient discomfort, severe pain, aseptic necrosis, and/or arthritis of the carpal bones. Surgical treatment of these conditions have included intercarpal fusion, arthroplasty, wrist fusion, local resection, proximal row carpectomy, bone grafting, radial styloidectomy, radial shortening or ulnar lengthening, and interposition arthroplasty. Among these processes, fusion procedures are not generally preferred. Although pain may be relieved, the stability, power and mobility of the joint are affected. Local resection procedures involving the removal of an irreversibly pathological bone result in instability and migration of adjacent carpal bones into the space left after the resection. This migration causes in instability in the wrist joint. In addition, metallic and ceramic implants developed for replacement of carpal bones have not been satisfactory due to problems relating primarily to, migration of the implant, implant loosening and absorption of bone due to hardness of the material inserted and poor force distribution.
Arthritis is one of the most prevalent causes of adult impairment affecting the small joints of the hand and wrist. Disability results from the grinding of adjacent bones whose natural articular surfaces are stripped of slippery cartilage and become rough from disease. One form of the disease is particularly prevalent and debilitating. It causes the osteoarthritic degeneration of the thumb basal joint (which is also known as carpometacarpal (CMC) joint), and affects as many as half of all post-menopausal women. The CMC joint is where the saddle-shaped trapezium bone articulates with the first metacarpal bone allowing motion like that of a mechanical universal joint. An arthritic CMC joint becomes painful enough to limit everyday activity such as grasping or pinching. Symptoms can often be treated with physical therapy, rest, splinting or anti-inflammatory medication. If pain persists, surgery may be indicated to allow return to activities of normal daily living.
Interposition arthroplasty, the most commonly performed surgical procedure for treating CMC arthritis, has been in use since the early 1970's. Interposition arthroplasty is a procedure where a biologic or synthetic material is interposed between the bones once the degenerated joint surfaces are removed. The interpositional material serves as a short term cushion to prevent bone to bone contact and to provide a scaffold for heeling into a surgically created void.
Known surgical intervention for treatment of CMC arthritis begins with the removal of the diseased tissue. Usually the entire trapezium bone or a portion thereof is removed. To prevent the collapse of the first metacarpal bone into the space thus created, a wire pin is often used to align the base of the first metacarpal bone with the base of the index metacarpal. The pin serves as a temporary stabilizer. A tendon, such as the palmaris longus or flexor carpi radialis is harvested from the forearm and rolled up, resembling a rolled “anchovy” or jelly-roll. The anchovy is then sutured to prevent unrolling and is interposed between the base of the thumb metacarpal and the scaphoid (the space previously occupied by the trapezium bone). In some cases, a suspensionplasty is performed wherein a further piece of tendon is used to tie the base of the thumb metacarpal to the base of the index metacarpal, thereby “suspending” the thumb metacarpal. The wire pin is left in place for about 4 to 6 weeks while healing occurs. It is usually 8 weeks or more before patients are allowed unrestricted activity.
Although the results of tendon interposition may be acceptable, there are a number of drawbacks to this procedure. As with any procedure requiring the use of a graft, there is additional surgical trauma and morbidity associated with the graft donor site. In many circumstances, there is not enough tendon available from which a graft may be harvested or the quality of the tissue is inadequate. Another major drawback is the amount of time it takes to harvest a tendon graft and prepare it for interpositional placement. Adding a suspensionplasty can also significantly increase operating time. There is evidence that during healing, the tendon grafts weaken and lose structural strength. Thus, the use of pins becomes necessary to help hold the thumb metacarpal in the right position until dense scar tissue forms that will ultimately support the metacarpal. Also, evidence shows that over the long term, thumb shortening and other anatomical changes may occur which have a deleterious effect on joint function and strength.
Prosthetic material has also been used to treat CMC arthritis. One widely used material has been silicone rubber. Several implant designs have been manufactured from these materials, including a cylindrical spacer with a long stem fitted into a canal formed into the metacarpal. Another design of silicone rubber implant comprises a button-shaped spacer with a small locating pin. Problems with fracture and dislocation of the aforementioned implants led to the development of other designs that incorporated a polyethylene terephthalate or polytetrafluoroethylene fabric mesh in order to improve strength and to allow tissue ingrowth for fixation to the metacarpal. Another implant contains a perforation to allow fixation by attaching a slip of the flexor carpi radialis tendon. However, all of these silicone rubber devices were subject to dislocation, fracture, abrasion and fatigue that led to the generation of small particles of silicone. The term “silicone synovitis” was coined to describe the chronic inflammatory reaction that resulted from this liberation of silicone particles.
There have been many attempts to address the problems associated with hard implants and degradation of silicone implants by designing two piece implants that were intended to reconstruct an articulating joint. Many of the early designs were basically a ball and socket joint on simple stems that require taking out or shaping multiple bones causing the surgery to be more complicated and invasive.
None of the described prosthetic interposition arthroplasty and CMC joint reconstruction devices have met with an acceptable degree of success. Problems are mostly associated with long-term breakdown, loosening, or dislocation. For these reasons tendon interposition with or without suspensionplasty has been used even despite the inherent problems associated with tissue graft harvesting, protracted operating room time and long term biomechanics, strength, function and deformity issues.
There is therefore a need for a trapezium bone implant for the carpometacarpal joint resurfacing implant, system and method of use that overcomes some or all of the previously delineated drawbacks of prior carpometarcarpal joint resurfacing implants.